Conventionally, there is known a vehicular seat capable of reducing burden or fatigue for the waist of a passenger (see Patent Literature 1).
As shown in FIG. 5, a seat device 100 incorporates a seat cushion frame 101 within a seat cushion. In this seat cushion, a substantially rectangular cushion plate 103 is suspended by a plurality of coil springs 102 whose one end is connected to the left or right side wall of the seat cushion frame 101. A seat back frame 104 constituting a seat back and the seat cushion frame 101 are provided rotatably through a hinge 106. The hinge 106 is equipped with a recliner 105 which permits the inclining angle of the seat back for the seat cushion to be adjusted.
In the seat back frame 104, vertically extending brackets 108 are provided through guide rail brackets 107. Back plates 109 are provided slidably along the brackets 108. Connecting members 110 are provided between the lower end of the back plates 109 and the rear of the cushion plate 103.
Therefore, when the cushion plate 103 supporting a seating area is vertically displaced, the back plates 109 are also moved vertically through the connecting members 110. Thus, the waist supporting area moves together with the back supporting area. Accordingly, in the vicinity of a waist area, slippage does not occur between the passenger and seat back, thereby permitting the fatigue of the waist to be reduced.
Patent Literature 1: Japanese Patent Unexamined Publication No. JP-A-8-205958 (FIG. 3).
Meanwhile, in the seat device 100 disclosed in Patent Literature 1, a cushion material such as an urethane pad is placed on areas of the seat cushion and seat back in contact with the passenger thereby to assure good riding comfort. However, it has been desired to further improve the holding quality for holding the posture of the passenger.